The present invention relates generally to high current opening switches, and more specifically to a very low inductance, very low resistance, command operated repetitive high current opening switch for railguns.
Railguns are being considered as a primary component of a space based ballistic missile defense system. One of the limiting components in a railgun system is the opening switch. The opening switch is required to conduct high currents for long periods of time and then quickly open to commutate, or switch, current into the railgun. In addition, the opening switch must be able to operate repetitively.
Railguns operate by using a very high electric current to create a very strong magnetic field. The vector cross product of the magnetic field with the current is called a Lorentz force. The Lorentz force will propel an electrically conductive projectile between a pair of electrically conductive rails. The projectile experiences several 100,000's of g's as it accelerates down the railgun barrel and can obtain muzzle velocities of several kilometers per second.
The very high railgun currents place tremendous energy dissipation demands on the opening switch. The amount of switching energy dissipated by the opening switch is primarily a function of the switch inductance. The prior art includes actual and proposed railgun opening switches of successively lower switch inductances, but even longer switch inductances will be required to increase the system efficiencies of space based rapid fire railguns. An example of an improved very low inductance opening switch is shown in the inventor's co-pending patent application Ser. No. 06/861,899, filed May 12, 1986, for a rotary opening switch, now U.S. Pat. No. 4,738,181, incorporated by reference as if fully rewritten herein.
Another factor affecting the amount of switching energy to be dissipated by the opening switch is its resistance to current flow. A lower resistance both increases the overall efficiency of the system and reduces the amount of heat to be dissipated by the switch. Prior art switches generally use brushes to conduct current. Despite many improvements in brush design, such as the use of finger brushes as described in the aforementioned co-pending patent application, brushes are inherently limited in how low a resistance they can provide at very high currents.
The need for repetitive operation capability has been satisfied in the prior art primarily by using rotating opening switches. Such switches, however, may be switched on and off only at set rates according to their rates of rotation. Further, such rotary switches start sluggishly and stop slowly.
It is thus seen that there is a need for a railgun opening switch of very low switch inductance, very low switch resistance and capable of being switched on and off at variable rates on command.
It is, therefore, a principal object of the present invention to provide a very low inductance, very low resistance, command operated repetitive railgun opening switch.
It is a feature of the present invention that it will work in any orientation relative to the rails.
It is another feature of the present invention that it may include a hollow center coaxial with the projectile path to allow breech loading and preacceleration of the projectile.